Abstract

The authors report on the first experimental demonstration of active feedback suppression of rotating external kinkmodes near the ideal wall limit in a tokamak using Kalman filtering to discriminate the kinkmode from background noise. The Kalman filter contains an internal model that captures the dynamics of a rotating, growing mode. Suppression of the external kinkmode is demonstrated over a broad range of phase angles between the sensed mode and applied control field, and performance is robust at noise levels that render proportional gain feedback ineffective. Suppression of the kinkmode is accomplished without excitation of higher frequencies as was observed in previous experiments using lead-lag loop compensation [A. J. Klein et al., Phys Plasmas12, 040703 (2005)].